EAST MEETS WEST TO STUDY SPACE STORMS
UK scientists are eagerly awaiting a late Christmas present with the launch of the first Double Star spacecraft, a pioneering European-Chinese space mission to explore the impact of solar storms on near-Earth space.
Known as Tan Ce (Explorer) 1, the spacecraft is scheduled to lift off from Xichang spaceport in southern China at 19:23 GMT on 27 December (03:23 on the 28 December in China). A second spacecraft will be launched on a Chinese Long March 2C rocket about six months later.
Double Star is the first Chinese mission dedicated to space science, and the first international space mission involving China. This unique collaboration between Europe and China will revolutionise our knowledge of the Earth's magnetosphere - the huge, tadpole-shaped region of space dominated by our planet's magnetic field - and its struggle to protect our planet from the supersonic particles that stream towards us from the Sun.
European institutes contribute eight of the 16 Double Star scientific instruments and part of the network of data systems on the ground. These instruments are almost identical to some of those which have been flying on the European Space Agency's Cluster quartet since the summer of 2000.
The four identical Cluster spacecraft - Rumba, Salsa, Samba and Tango - fly around the Earth in close formation to carry out unique 3-D observations of the electrically charged particles in the solar wind and their battle with the magnetosphere.
The arrival of Double Star will complete an unprecedented squadron of six spacecraft in near-Earth space. The sextet will conduct a synchronised orbital dance around the Earth, studying the link between the solar wind and geomagnetic activity, and providing the most detailed, multi-dimensional view of the complex magnetosphere ever obtained.
Whilst the Cluster spacecraft are separated by only a few hundred kilometres, Double Star will be tens of thousands of kilometres apart. Whilst Cluster is observing magnetic fields and particles far from the Earth, Double Star will be making simultaneous measurements much closer to home.
"On its own, Double Star would be scientifically important because it will provide new measurements in key regions of magnetosphere," said Andrew Fazakerley (MSSL-UCL), one of the Principal Scientific Investigators (PIs) from the UK. "For example, it will provide important new information on the Earth's changing radiation belts."
"However, the really exciting part is that the orbits of the two spacecraft are explicitly designed for co-ordinated measurements with Cluster," he added. "So, when Cluster is in the distant magnetic tail and Double Star is in the near tail, we shall be able to see simultaneously for the first time what happens in both of these key regions when the huge amounts of energy that drive the aurora are released."
"Similarly, when Double Star is on the dayside of the Earth and Cluster is passing over the poles, we'll be able to observe what happens in several key regions at once, as the solar wind transfers some of its energy to the magnetosphere, leading to aurorae and changes in the radiation belts around the Earth."
UK teams play major roles in both Double Star and Cluster, both through provision of instruments and in science operations.
Each Double Star spacecraft is a spinning cylinder about 2 metres across and 1 metre high. Seven of the eight European instruments on the pair of Double Star spacecraft (including five led by the UK) are copies of instruments on Cluster.
Principal Investigator for the Fluxgate Magnetometer (FGM) experiments on TC-1 and TC-2 is Chris Carr from the Cluster team at Imperial College London. These instruments can measure a magnetic field in space 1,000 times weaker than the field at the Earth's surface.
The Plasma Electron and Current Experiment (PEACE) on TC-1 and TC-2 was provided by the Cluster team at Mullard Space Science Laboratory, led by Andrew Fazakerley. This measures the speed, direction and population of electrons around the spacecraft.
An experiment on TC-1 that measures waves (rapid variations in the magnetic field) includes the Digital Wave Processor (DWP) instrument, developed by the Cluster team at the University of Sheffield, under the leadership of Hugo Alleyne.
In addition, Double Star will draw on science operations expertise at the Rutherford Appleton Laboratory (RAL). RAL has been running the Cluster Joint Science Operations Centre (JSOC) since the beginning of 2001 and has adapted this to provide a similar service for Double Star. This European Payload Operations Service (EPOS) will work with the European instrument teams on Double Star to co-ordinate the commanding of their instruments and will deliver the finalised commanding to the Double Star Science Application System in Beijing.
RAL is also providing the Double Star Data Management System that will exchange key data products between national data centres in Austria, France and the UK, and enable users of those centres to browse and retrieve those products.
"I'm looking forward to planning simultaneous observations by Double Star and Cluster," said Mike Hapgood, lead scientist for both the Cluster JSOC and Double Star EPOS. "This is a great opportunity to advance our understanding of the large-scale behaviour of the Earth's magnetosphere."
NOTES FOR EDITORS
Double Star is the first major collaboration between Europe and China on a scientific space mission. A major challenge has been to compare the methods used to develop space missions in Europe and China and to develop efficient ways of working together.
Tan Ce 1 (TC-1) will fly in a highly elliptical equatorial orbit of 550 x 63,780 kilometres (340 x 39,860 mls), inclined at 28.5° to the equator. Over a lifetime of at least 18 months, it will sample key regions on the day and night sides of the Earth where the process of magnetic reconnection occurs. These reconnection processes dominate the dynamics of the magnetosphere.
Tan Ce 2 (TC-2) will fly in a highly elliptical polar orbit of 700 x 39,000 kilometres (440 x 24,375 mls). Over a period of one year, it will sample the polar cap and cusp regions. These are the main regions where energy from the Sun flows into the magnetosphere. Those energy flows are largely controlled by the reconnection processes to be studied by TC-1.
In order to allow the combined observations by six spacecraft, the lifetime of ESA's Cluster mission has been extended three years until the end of 2005.
The turbulent interaction between the supersonic solar wind and Earth's protective magnetic shield is revealed in various ways. The arrival of huge clouds of magnetised particles (known as coronal mass ejections) at the Earth gives rise to the beautiful aurorae - the Northern and Southern Lights - but it can also produce magnetic storms that may have serious consequences for human activities, from power cuts to damaged satellites and communication breakdowns.
FURTHER INFORMATION CAN BE FOUND AT:
Double Star (ESA):
Chinese National Space Administration:
Rutherford Appleton Laboratory (Cluster / Joint Science Operations Centre):
Date: 22 December 2003
Issued by Peter Bond, RAS Press Officer (Space Science).